A horror movie about a horror movie about horror movies!
Scream gets a little more grandiose, graciously moving its plot and its survivors to Hollywood. The main protagonists are adults, now, and they have been through a lot. The tone is consequentially dark, but spiced up by the re-introduction of stereotypical characters and surreal settings. The action mostly takes place on the set of a film inspired by the events of the two first Scream movies.
By tradition, the new faces are either used as slasher meat, red herrings or both. Guessing the killer's identity is harder than ever, the characters having been left underdeveloped and the amount of speaking roles having increased. Scream purists will find the script clustered, superficial, and cold when it comes to dialogue. This one isn't big on details and human chemistry.
The previous film was a self-referential sequel; the third one focuses on the rules of trilogies. The game, then, becomes to second-guess the outcome, based on our personal fandom knowledge or hints left by the franchise, so far. As stated in Scream 3, for better or worse, anything goes in this one. It won't rub everybody the right way, but it's still a brilliantly directed high-budget slasher.